M.Sc. Sedlák J. PhD.1, Prof. M.Sc. Píška M. PhD.1, M.Sc. Ptáčková M. 1, M.Sc.MadajM.1, M.Sc. Charvát O. 1, M.Sc. Dvořáček J. 1, M.Sc. Zouhar J. PhD.1, M.Sc.Rozkošný L.2
Faculty of Mechanical Engineering – Brno University of Technology, the Czech Republic 1
Innomia Company, Inc., the Czech Republic 2
Abstract: Direct Metal Laser Sintering1 (DMLS) is a revolutionary technology that allows a production of fully functional metal parts directly from a 3D CAD data, eliminating the investment to production tools and technologies which brings considerable cost and time savings. Metal parts made by DMLS technology are fully comparable with casted or machined parts. A range of application of DMLS technologies is very wide – from prototypes, through short-run production to final products. Advantages of DMLS technology are arising along with complexity of parts – more complex geometry of parts (in terms of shape and occurrence of the detail) make DMLS technology even more economically effective.
Keywords: TITANIUM ALLOY, DMLS, LASER SINTERING, 3D PRINTING, MICROSTRUCTURE
1. Introduction
A 3D CAD data of a part are imported into the procedural software of the printer EOSINT M 2701. Software designed to the data preparation allows choosing the appropriate thickness of production layers with regard to accuracy / resolution and speed of production (0.020 mm or 0.040 mm ‒ thinner layer means higher accuracy, but longer production time).
After the selection of powdered material (including the thickness of the layer) software assigns the proper technological parameters of construction and "cuts" the 3D data into layers which sends to the 3D printer EOSINT M 270. A steel platform is clamped into the working chamber of the 3D printer which has a function of a basement for the part constructing (Fig. 1). Afterwards, a dosing device sets the quantity of powder needed for one layer and then a shoulder with a ceramic blade spread on the surface of the steel platform a uniform layer of powder according to the chosen layer thickness. In the impact point of a laser beam, the powder is locally melted; the base layer is “melted-through” and then it solidifies into the solid state.
Fig. 1 Working principle of 3D the printer EOSINT M 2701.Energy of the laser beam locally melts the metal powder1 only in contour of the cut which is defined by the intersection of the plane (layer) of the product body (3D CAD model). A correct position of the part is very important during a fabrication. The supporting structure (anchored on the base steel platform) is used
to ensure the correct part position. Metal powder is thoroughly melted by the laser and ensures a perfect close coupling of deposited layers. Powerful 200 Ytterbium (Yb)-fiber “dual-spot” laser is able to produce even small construction features in fine resolution, fabrication of the physical model is faster thanks to the higher energy density of the laser beam. The laser beam is precisely driven in the X and Y coordinates, Z-axis is controlled by shifting of the platform layer when the layer is created. This system allows accordance with geometrical tolerances of shape in the range of
± 0.1 mm. Workspace of 3D printer EOSINT M270 is 250 x 250 x 215 mm.
2. Materials for Production of Prototype Parts1
A wide range of metal powders (from light alloys through steels to super-alloys and composites) is currently available for DMLS process and other new materials are under development. Table 1 lists mechanical properties of selected powder materials.
Table 1: Mechanical properties of selected powder materials1. *Note: Values in brackets are valid for heat-treated material.
Stainless steel EOS GP1 / Martensitic steel EOS MS 1 / Bronze-nickel alloy DM 20Min. wall thickness [mm] / 0,4 / 0,4 / 0,6
Speed of fabrication [mm3/min-1] / 2-5 / 2-4 / 10-20
Residual porosity [%] / - / - / 8%
Yield strength Rm [MPa] / 900 / 1100 (1950*) / 400
Proof stress Rp0,2 [MPa] / 500 / 1000 (1900*) / 200
Modulus of elasticity [GPa] / 190 / 180 / 80
Abrasive hardness / 23-33 HRC / 36-39 (50-54*) HRC / 120 HV
Max. working temp. [°C] / 550 / 400 / 400
Titanium EOS Ti64 / Ti64ELI
Subject of research was TiAl6V4 alloy in the form of the fine powder. This light alloy (see Fig. 2) has excellent mechanical properties Tab. 2 and corrosion resistance in combination with low specific weight and biocompatibility. The material is mainly used
in aviation, in the manufacturing of racing cars and in medical applications (manufacturing of implants, see Fig. 3).